Electronic Supporting Information Elucidating the Mechanism ...S1 Electronic Supporting Information Elucidating the Mechanism of the Ley-Griffith (TPAP) Alcohol Oxidation Timothy J.
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Electronic Supporting Information
Elucidating the Mechanism of the Ley-Griffith (TPAP) Alcohol Oxidation
Timothy J. Zerk,a Peter W. Moore,a Joshua S. Harbort,b Sharon Chow,a Lindsay Byrne,c George A. Koutsantonis,d Jeffrey R. Harmer,b Manuel Martínez,e Craig M. Williamsa,* and Paul V. Bernhardta,*
a School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072,
Queensland, Australia b Centre for Advanced Imaging, University of Queensland, Brisbane 4072, Australia
c Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Crawley,
Western Australia 6009, Australia d School of Molecular Sciences, University of Western Australia, Crawley, Western Australia 6009,
Australia e Departament de Química Inorgànica I Orgànica, Secció de Química Inorgànica, Universitat de
Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain
A stock suspension of ruthenium dioxide was prepared by adding a stoichiometric amount of
isopropanol to a concentrated solution (25.0 mM) of perruthenate in acetonitrile. Within minutes
the dark green solution turned brown but the reaction was allowed to continue at 303 K for one
hour to ensure quantitative formation of insoluble RuO2·2H2O. Previous work has demonstrated that
in organic solvent, secondary alcohols are oxidised by a stoichiometric quantity of perruthenate to
give the ketone (in this case acetone) and RuO2·2H2O.4 An aliquot of the stock suspension was added
to one of two pre-prepared cuvettes containing n-Pr4N[RuO4] and NMO which were already
thermostatted in the spectrometer at 303 K and the two reactions were initiated by a final addition
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of diphenylmethanol. Acetone from the stock solution of the dioxide has no effect as it is an inert
solvent which can itself be used for these oxidation reactions.4
Figure S1. Experimental apparatus used to synthesise TPAP. Setup is shown post-reaction. Flask A contains TPAP product in solution.
A B
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Figure S2. Maximum rate of oxidation during the induction and catalytic periods is determined by the slope of the steepest tangent within each region. Experimental conditions are identical to Figure 1 A.
0 10000 20000 300000
5
10
15
[Be
nzo
ph
en
on
e] / m
M
Time / s
slope = vmax-cat
slope = vmax-ind
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Figure S3. Time resolved spectra from Figure 1 with the constant spectrum of n-Pr4N[RuO4] subtracted. Inset – benzophenone concentration versus time profile.
300 350 400 450 500 5500.0
0.5
1.0
1.5
2.0
Ab
so
rba
nce
/ a
.u.
Wavelength / nm
0 10000 20000 300000
5
10
15
[Be
nzo
ph
en
on
e]
/ m
M
Time / s
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200 300 400 500 6000.0
0.5
1.0A
bso
rba
nce
/ a
.u.
Wavelength / nm
Figure S4. Time-resolved spectra following 0.25 mM n-Pr4N[RuO4] in MeCN + 150 mM NMO over the course of seven hours (303 K). Spectra recorded every ten minutes. The spectrum is identical throughout to that of n-Pr4N[RuO4] in MeCN.
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Figure S5. X-band (νav = 9.6766 GHz) CW EPR spectra measured at 6 K showing the decay of perruthenate EPR signal over time after addition of substrate alcohol in the absence of co-oxidant NMO.
3300 3400 3500 3600 3700 3800
Field / Gauss
0 mins
1 min
2 mins
3 mins
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18O Labelling of piperonol and its Ley-Griffith Oxidation
Mass spectral data Identified the starting material to be 78% 18O-enriched piperonol. After
Ley-Griffith oxidation the MS data of product piperonal comprised a mixture of its molecular ion M
and M-1 due to H-atom fragmentation at the aldehyde. Coupled with the mixture of 18O and 16O
isotopomers derived from the 78% enriched starting material this leads to four possible compounds:
(m/z 152) (Figure S7, S8). The 18O:16O isotopic ratio was 83/38 (68% 18O enriched). Given the
uncertainties in the mass spectral intensities, there is no significant change in the isotopic ratio going
from piperonol to piperonal.
Figure S6. Mass spectra of the 18O-enriched piperonal product after Ley-Griffith oxidation. Various relevant structures on following page.
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Mass fragmentation pattern with piperonol and piperonal.
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Figure S7. Time-resolved spectra following the oxidation of 6.0 mM diphenylmethanol by 0.25 mM n-Pr4N[RuO4] (commercial, 97% pure) and 60 mM NMO in MeCN (303 K). Spectra are displayed at five minute intervals. Inset – Single wavelength profile at 336 nm.
300 400 5000.0
0.5
1.0
1.5
2.0
0 5000 10000 15000
0.5
1.0
1.5
2.0
Ab
so
rba
nce
/ 3
36
nm
Time / s
Abso
rba
nce
/ a
.u.
Wavelength / nm
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Figure S8. 1.8 mg of n-Pr4N[RuO4] in MeCN (10 mL). Left – synthesised; Right ̶ commercial.
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References
1. D. D. Perin and L. F. Armarego, Purification of Laboratory Chemicals, 3rd edn., Pergamon Press, Oxford, England, 1988.
2. W. P. Griffith, S. V. Ley, G. P. Whitcombe and A. D. White, J. Chem. Soc., Chem. Commun., 1987, 1625-1627.
3. W. Lin, L. long, D. Peng and C. Guo, J. Organomet. Chem., 2007, 692, 1619-1622. 4. A. C. Dengel, R. A. Hudson and W. P. Griffith, Transition Met. Chem., 1985, 10, 98-99.